Heat Exchanger Plate, A Pair Of Two Heat Exchanger Plates, And Plate Package For A Plate Heat Exchanger

ABSTRACT

The invention refers to a heat exchanger plate ( 11 ), a pair of heat exchanger plates, and a plate package for a plate heat exchanger. Each heat exchanger plate includes a heat transfer area ( 33 ) and a distribution area ( 34 ) which adjoins the heat transfer area along a borderline ( 35 ). The distribution area has projections and depressions abutting depressions and projections, respectively, on a distribution area of adjacent heat exchanger plates. The heat transfer area has projections ( 51 ) and depressions ( 52 ) abutting depressions and projections, respectively on a heat transfer area of adjacent heat exchanger plates for forming first contact surfaces positioned at a first distance from each other along a direction substantially parallel with the borderline. The heat transfer area includes a transition area ( 58 ), which adjoins the distribution area along the borderline and has projections and depressions abutting depressions and projections, respectively, of a heat transfer area of adjacent heat exchanger plates for forming second contact surfaces at a second distance from each other along the first direction. The second distance is significantly shorter than the first distance.

THE BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention refers to a heat exchanger plate for a platepackage for a plate heat exchanger according to the preamble of claim 1.The invention also refers to a pair of heat exchanger plates comprisinga first heat exchanger plate and a second heat exchanger plate accordingto the preamble of claim 8. Furthermore, the invention refers to a platepackage for a plate heat exchanger according to the preamble of claim17.

Such plate heat exchangers with heat exchanger plates of the initiallydefined kind comprise commonly a central heat transfer area with aso-called herringbone pattern, which means that the corrugations of aparallel ridges and valleys of adjacent plates abut each other in such away that substantially point-shaped contact surfaces are formed betweenthe plates, and with distribution areas at the portholes on the endareas of the heat exchanger plates. The distribution areas are commonlyprovided with so-called distribution patterns (“chocolate patterns”),i.e. the corrugations of adjacent plates are designed in such a way thatthey form substantially line shaped contact surfaces between adjacentplates. In the transition between the distribution area and the centralheat transfer area, i.e. where the corrugation patterns change design,the strength becomes somewhat reduced than at the central heat transferarea proper and the distribution areas proper. The reason therefor isthat the different construction methods of the corrugation patterns,which means that the herringbone pattern has many small closelypositioned contact surfaces whereas the distribution pattern has largebut few contact surfaces with a free structure therebetween.

FIG. 1 discloses schematically a heat exchanger plate 1 where, in anarea at the top to the right, a pattern has been drawn in the transitionbetween the central heat transfer area 2 and the distribution area 3. InFIG. 2 this area is shown in a larger scale. The rhomboids 4 correspondto the line-shaped contact surfaces at the bottom plane of the heatexchanger plate 1 and the rhomboids correspond to the line-shapedcontact surfaces at the upper plane of the heat exchanger plate 1. Thelines 6 are valleys of the heat exchanger plate 1 concerned whereas thelines 7 are the ridges of an adjacent heat exchanger plate 1. Where thevalleys 6 cross the ridges 7 point-shaped contact surfaces are created,which absorbs pressure load. In FIG. 2, the herringbone pattern of thecentral heat transfer area 2 is a typical so called pattern with highNTU (Number of Heat Transfer Units) with an acute angle of approximately65° between the ridges and a centre axis x in the longitudinal directionof the heat exchanger plate 1. FIG. 3 discloses a typical so calledpattern with low NTU with a corresponding acute angle of approximately25°. The pattern with high NTU gives a relatively high flow resistancewhereas the pattern with low NTU gives a relatively low flow resistance.

The pattern with high NTU gives the distance A1 along the width betweenthe contact surfaces, which is significantly larger than thecorresponding distance A2 of the pattern with low NTU. In the transitionto the distribution area, this is of great importance for the strengthsince the contact surfaces have to take a part of the load on thedistribution area. If the distance A1 is compared with A2 it can be seenthat A1 is twice as long as A2. Since the number of contact surfaces inthe row is reciprocally proportional to the distance, the pattern withlow NTU will give twice as many support points as the pattern with highNTU along the transition to the distribution area. The longer thedistance along the width between the contact surfaces is, the larger theload on each contact surface will be, and it is difficult to avoid largefree surfaces which are highly loaded. In addition to a higher load onthe contact surfaces on the pattern with high NTU, a collapsing load forthe fields in the distribution area also becomes lower.

The heat exchanger plate with pattern with high NTU on the central heattransfer area will thus determine the maximal pressure performance forthe heat exchanger plates in the cases when this area is dimensioning.If the heat exchanger plates always are provided with a pattern with lowNTU on the central heat transfer surface, the above mentioned strengthproblems will not occur. However, in many cases it is desirable to use aso-called pattern with high NTU on the central heat transfer area inorder to obtain a high heat transfer.

U.S. Pat. No. 4,781,248 discloses a heat exchanger plate of theinitially defined type. This heat exchanger plate is intended to beincluded in a plate package for a plate heat exchanger. It is especiallyreferred to FIG. 4 in this document, which discloses a distribution areawith a distribution pattern and a central heat transfer area with apattern with high NTU.

SUMMARY OF THE INVENTION

The object of the present invention is to avoid the problem mentionedabove at the transition between the distribution area and the centralheat transfer area. More precisely, the object is to provide an improvedstrength at the transition between the distribution area and the centralheat transfer area.

This object is achieved by the heat exchanger plate initially defined,which is characterized in that the central heat transfer area comprisesat least a first transition area, which adjoins the first distributionarea along the borderline and which has projections and depressionswhich are adapted to abut depressions and projections, respectively, ofa central heat transfer area of adjacent heat exchanger plates in theplate package for forming second contact surfaces which are positionedat a second distance from each other along said direction which issubstantially parallel with the borderline, wherein the second distanceis significantly shorter than the first distance.

By such a transition area substantially more support points betweenadjacent plates are achieved in the proximity of the distribution areaso that the plate package in a better way may resist the load which theplate package is subjected to during operation. The support points alonga line in parallel with the borderline will be substantially moreclosely positioned and thus substantially more than according to thepreviously known technique, in particular when the central heat transferarea has a so called pattern with high NTU.

According to an embodiment of the invention, the central heat transferarea has a corrugation, which forms said projections and depressions andwhich extends along a direction forming an acute first angle with thecentre axis, wherein the first transition area has a corrugation, whichforms said projections and depressions and which extends in a directionforming an acute second angle with the centre axis, and wherein thefirst angle is significantly larger than the second angle. The patternof the transition area may according to this embodiment be designed as aherringbone pattern with a relatively low flow resistance, i.e. aso-called pattern with low NTU.

According to a further embodiment of the invention, at least some of thesecond contact surfaces are provided along at least one line extendingin parallel with the borderline and located at a distance from theborderline, which distance is relatively small and significantly shorterthan the second distance. In such a way, the support points betweenadjacent heat exchanger plates will be positioned close to thedistribution area and contribute to an improved strength in this part ofthe heat exchanger plate.

According to a further embodiment of the invention, said directionextends substantially perpendicularly to the centre axis.

According to a further embodiment of the invention, the projections anddepressions of the transition area are designed in such a way that thesecond contact surfaces obtain an approximate point-shape when the heatexchanger plate is provided in the plate package adjacent to anotherheat exchanger plate.

According to a further embodiment of the invention, the projections anddepressions of the distribution area are adapted to abut depressions andprojections, respectively, of adjacent heat exchanger plates in theplate package for forming third contact surfaces. Furthermore, theprojections and depressions of the distribution area may be designed insuch a way that the third contact surfaces obtain an approximateline-shape when the heat exchanger plate is provided in the platepackage adjacent to another heat exchanger plate. Such a design includesa so called distribution pattern.

The object is also achieved by the initially defined pair of heatexchanger plates, which is characterized in that the central heattransfer area of at the least the first heat exchanger plate comprisesat least a first transition area, which adjoins the first distributionarea along the borderline and which in relation to the extension planehas projections and depressions which are adapted to abut depressionsand projections, respectively, of a central heat transfer area of thesecond heat exchanger plate for forming second contact surfaces whichare positioned at a second distance from each other along said firstdirection which is substantially parallel with the borderline, whereinthe second distance is significantly shorter than the first distance.

Preferred embodiments of this pair of heat exchanger plates are definedin the dependent claims 9-16.

Furthermore the object is achieved by the initially defined platepackage which is characterized in that the central heat transfer area ofat least the first heat exchanger plates comprises at least a firsttransition area, which adjoins the first distribution area along theborderline and which in relation to the extension plane has projectionsand depressions which are adapted to abut depressions and projections,respectively, of a central heat transfer area of the second heatexchanger plates for forming second contact surfaces which arepositioned at a second distance from each other along said firstdirection which is substantially parallel with the borderline, whereinthe second distance is significantly shorter than the first distance.

Preferred embodiment of the plate package are defined in the dependentclaims 18-25.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now to be explained more closely through adescription of various embodiments and with reference to the drawingsattached hereto.

FIG. 1 discloses schematically a plan view of a heat exchanger plateaccording to the prior art.

FIG. 2 discloses more closely an area at the top to the right of theheat exchanger plate in FIG. 1.

FIG. 3 discloses the area in FIG. 2 with an alternative pattern.

FIG. 4 discloses schematically a side view of a plate heat exchangerwith a plate package of heat exchanger plates.

FIG. 5 discloses schematically a front view of the plate heat exchangerin FIG. 4.

FIG. 6 discloses schematically a plan view of a heat exchanger plate forthe plate package and the plate heat exchanger in FIGS. 4 and 5.

FIG. 7 discloses schematically an area of two adjacent heat exchangerplates according to a first embodiment.

FIG. 8 discloses schematically an area of two adjacent heat exchangerplates according to a second embodiment.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

FIGS. 4 and 5 disclose a plate heat exchanger according to the inventionfor receiving a first medium and a second medium. The plate heatexchanger comprises a plate package 10 with a number of heat exchangerplates 11 which are provided adjacent to each other. The plate package10 is provided between a frame plate 12 and a pressure plate 13. Thepressure plate 13 is pressed against the plate package 10 and the frameplate 12 by means of tie bolts 14 which extend through the plates 12 and13. The tie bolts comprise threads and the plate package may thus becompressed by threading a nut 15 on the tie bolts 14 in a manner knownper se. In the embodiment disclosed, four tie bolts 14 are indicated. Itis to be noted that a number of tie bolts 14 can vary and be differentin various applications. It is also to be noted that even if thefollowing description refers to plate heat exchangers provided withgaskets and compressed by means of tie bolts or the like, the inventionis also applicable to plate heat exchangers having permanently joinedheat exchanger plates, for instance brazed plate heat exchangers. Theinvention may also be applied to plate heat exchangers having pairs ofpermanently joined heat exchanger plates, where two heat exchangerplates for instance may be welded to each other.

The plate heat exchanger comprises a first inlet 20 for the firstmedium, a first outlet 21 for the first medium, a second inlet 22 forthe second medium and a second outlet 23 for the second medium. Theinlets and outlets 20-23 extend through the frame plate 12 and the platepackage 10.

FIG. 6 discloses a heat exchanger plate 11 for the plate heat exchangerin FIGS. 4 and 5. The heat exchanger plate 11 is compression-moulded andextends along a central extension plane p-p, see FIG. 4. The heatexchanger plate 11 comprises a first end area 31, a second end area 32and a central heat transfer area 33, which extends between and adjoinsthe first end area 31 and the second end area 32. A centre axis xextends along the heat exchanger plate 11 in the central extension planep-p through the first end area 31, the central heat transfer area 33 andthe second end area 32.

A first distribution area 34 extends on the first end area 31 andadjoins the central heat transfer area 33 along a first borderline 35. Asecond distribution area 36 extends on the second end area 32 andadjoins the central heat transfer area 33 along a second borderline 37.In the embodiments disclosed, the borderlines 35 and 37 aresubstantially perpendicular to the centre axis x. It is to be noted,however, that the borderlines 35 and 37 may have a certain inclinationin relation to the centre axis x, may be curved or extend in differentdirections along different portions of the borderlines 35, 37.

Each heat exchanger plate 11 also comprises four portholes 41, 42, 43and 44 for the inlets and outlets 20-23. The portholes 41 and 44 areprovided on the first end area 31 and the portholes 42 and 43 on thesecond end area 32. Between each pair of heat exchanger plates 11, afirst gasket 45 is provided for defining a first plate interspace forthe first medium between two adjacent heat exchanger plates and a secondplate interspace for the second medium between two adjacent heatexchanger plates 11. The first plate interspaces communicate with thefirst inlet 20 and the first outlet 21 via two of the portholes 41-44.The second plate interspaces communicate with the second inlet 22 andthe second outlet 23 via two of the portholes 41-44.

The central heat transfer area 33 has in relation to the centralextension plane p-p a pattern or a corrugation of projections 51 anddepressions 52, which form parallel ridges and valleys and are adaptedto abut depressions 52 and projections 51, respectively, on a centralheat transfer area 33 of adjacent heat exchanger plates 11 in the platepackage 10 in such a way that first contact surfaces 54 are formedbetween the projections 51 and depressions 52. In FIGS. 7 and 8 this isillustrated by the projections 51 of one heat exchanger plate 11 whichabut and cross the depressions 52 of an adjacent heat exchanger plate11.

In the embodiments disclosed, the corrugation of parallel projections 51and depressions 52 of the central heat transfer area 33 extend in adirection forming an acute first angle α with the centre axis x, seeFIG. 6. With such a corrugation of parallel ridges and valleys, thefirst contact surfaces 54 will obtain an approximate point shape whenone of the two adjacent heat exchanger plates 11 is turned 180° in thecentral extension plane p-p, see FIGS. 7 and 8. The pattern ofprojections 51 and depressions 52 of the central heat transfer area 33is in the embodiments disclosed designed as a so-called herringbonepattern. The first contact surfaces 54 are positioned at a firstdistance A3 from each other along a direction, which in the embodimentdisclosed in FIG. 7 is substantially parallel with the borderline 35 andthus substantially perpendicular to the centre axis x. In the embodimentdisclosed in FIG. 8, a corresponding direction forms an acute angle withthe borderline 35.

The central heat transfer area 33 also comprises a first transition area58 which adjoins the first distribution area 31 along the borderline 35,and a second transition area 59, which adjoins the second distributionarea 32 along the borderline 37. Each of the first and second transitionareas 58, 59 has in relation to the central extension plane p-p apattern or a corrugation of projections 61 and depressions 62. Theseprojections 61 and depressions 62 are adapted to abut depressions andprojections, respectively, of a central heat transfer area 33 of anadjacent heat exchanger plate 11 in such a way that second contactsurfaces 64 are formed. The depressions and projections of the centralheat transfer area 33 of the adjacent heat exchanger plate 11 may thenbe formed by either the depressions 62 and projections 61 of atransition area 58, 59 of the central heat transfer area 33 of theadjacent heat exchanger plate 11, see FIG. 7, or of the depressions 52and projections 51 of the central heat transfer area 33, see FIG. 8.

The first distribution area 34 and the second distribution area 36 bothhave in relation to the extension plane p-p also a pattern or acorrugation of projections 71 and depressions 72, which are adapted toabut depressions 72 and projections 71, respectively, of a distributionarea 34, 36 of adjacent heat exchanger plates 11 in the plate package 10for providing a uniform distribution of the respective medium conveyedfrom one of the port holes 41, 43 to the central heat transfer area 33or for conveying in a favourable manner the respective medium from thecentral heat transfer area 33 to one of the port holes 42, 44. Thedistribution areas 34, 36 are designed in such a way that the pattern ofprojections 71 and depressions 72 gives a relatively small flowresistance, especially in relation to the flow resistance of a centralheat transfer area 33 with a pattern with high NTU.

The projections 71 and depressions 72 of the distribution area 33 areadapted to abut depressions 72 and projections 71, respectively, ofadjacent heat exchanger plates 11 in such a way that third contactsurfaces 74 are formed between the projections 71 and the depressions72, which surfaces obtain an approximate line shape when a heatexchanger plate 11 is provided adjacent to another heat exchanger plate11 which is rotated 180° in the extension plane p-p. A pattern ofprojections 71 and depressions 72 of the distribution areas 34, 36 is inthe embodiments disclosed designed as a so-called distribution pattern.

The first transition area 58 and the second transition area 59 have arespective pattern or a respective corrugation, which forms saidprojections 61 and depressions 62 and which extends in a directionforming an acute second angle β with the centre axis x, see FIG. 6. Thesecond angle β is relatively small and may suitably be in the order of20-35°, for instance 25°.

In the embodiment disclosed in FIG. 7, the first angle α is relativelylarge, for instance in the order of 65°, i.e. substantially larger thanthe second angle β. Thus a so-called pattern with high NTU is obtainedi.e. a central heat transfer area 33 with a relatively high heattransfer and a relatively high flow resistance and pressure drop. Withsuch a large first angle α, a relatively large distance A3 between thecontact surfaces 54 is achieved, and the initially defined problems withthe strength at the transition between the distribution area 34, 36 andthe central heat transfer area 33. This problem can be overcome with thetransition area 58, 59 disclosed. The second contact surfaces 64 of thetransition area 58, 59 are positioned at a second distance A4 betweeneach other along a direction which is substantially parallel to theborderline 35, 37. The second distances A4 are significantly shorterthan the first distances A3. Thus the number of support points betweenadjacent heat exchanger plates 11 is increased in the transition area58, 59 and hence the strength is improved.

Furthermore, some of the second point-shaped contact surfaces 64 areprovided along at least one line which extends in parallel with theborderline 35, 37 and is located at a distance B1 from the borderline35, 37, which distance is relatively small. Especially, the distance B1is significantly shorter than the second distance A4.

In the embodiment disclosed in FIG. 8, two types of heat exchangerplates are used, wherein one is provided with a transition area 58 whichhas another pattern design than the central heat transfer area 33whereas the other heat exchanger plate 11 has substantially the samepattern design on the transition area and the central heat transfer area33. More precisely, one of the heat exchanger plates 11 is designed insubstantially the same manner as the heat exchanger plates according tothe first embodiment disclosed in FIG. 7 whereas the other heatexchanger plate 11 has substantially the same design as the heatexchanger plates according to the prior art. The second heat exchangerplate 11, however, has a so-called pattern with a low NTU, i.e. thefirst angle α is relatively small and is equal to or substantially equalto the second angle β of the transition area 58 of the first heatexchanger plate 11.

The present invention is not limited to the embodiments disclosed butmay be varied and modified within the scope of the following claims.

1.-25. (canceled)
 26. A heat exchanger plate for a plate package (10)for a plate heat exchanger for receiving a first medium and a secondmedium, wherein the heat exchanger plate (11) has a central extensionplane (p-p) and comprises a first end area (31), a second end area (32),a central heat transfer area (33), which extends between the first endarea (31) and the second end area (32), wherein a center axis (x)extends along the heat exchanger plate through the first end area (31),the central heat transfer area and the second end area (32), and atleast a first distribution area (34) which extends on the first end area(31) and adjoins the central heat transfer area (33) along a borderline(35), wherein the distribution area (34) in relation to the extensionplane (p-p) has projections (71) and depressions (72) which are adaptedto abut depressions (72) and projections (71), respectively, on adistribution area (34) of adjacent heat exchanger plates in the platepackage for providing a uniform distribution of said media along theborderline (35), wherein the central heat transfer area (33) in relationto the extension plane (p-p) has projection (51) and depression (52)which are adapted to abut depressions (52) and projections (51),respectively, on a central heat transfer area (33) of adjacent heatexchanger plates in the plate package for forming first contact surfaces(54) which are positioned at a first distance (A3) from each other alonga first direction which is substantially parallel with the borderline(35), and wherein the central heat transfer area (33) comprises at leasta first transition area (58), which adjoins the first distribution area(34) along the borderline (35) and which in relation to the extensionplate (p-p) has projections (61) and depressions (62) which are adaptedto abut depressions (62, 52) and projections (61, 51), respectively, ofa central heat transfer area (33) of adjacent heat exchanger plates inthe plate package for forming second contact surfaces (64) which arepositioned at a second distance (A4) from each other along said firstdirection which is substantially parallel with the borderline (35),wherein the second distance (A4) is significantly shorter than the firstdistance (A3).
 27. A heat exchanger plate according to claim 26, whereinthe central heat transfer area (33) has a corrugation, which forms saidprojections (51) and depressions (52) and which extends along aninclination direction forming an acute first angle (α) with the centeraxis (x), wherein the first transition area (58) has a corrugation,which forms said projections (61) and depressions (62) and which extendsalong an inclination direction forming an acute angle (β) with thecenter axis (x), and wherein the first angle (α) is significantly largerthan the second angle (β).
 28. A heat exchanger plate according to claim26, wherein at least some of the second contact surfaces (64) areprovided along at least one line extending in parallel with theborderline (35) and located at a distance (B1) from the borderline (35),which distance is relatively small and significantly shorter than thesecond distance (A4).
 29. A heat exchanger plate according to claim 26,wherein said first direction extends substantially perpendicularly tothe center axis (x).
 30. A heat exchanger plate according to claim 26,wherein the projections (61) and the depressions (62) of the transitionarea (33) are designed in such a way that the second contact surfaces(64) obtain an approximate point shape when the heat exchanger plate isprovided in the plate package adjacent to another heat exchanger plate.31. A heat exchanger plate according to claim 26, wherein theprojections (71) and the depressions (72) of the distribution area (34)are adapted to abut depressions (72) and projections (71), respectively,of adjacent heat exchanger plates (11) in the plate package (10) forforming third contact surfaces (74).
 32. A heat exchanger plateaccording to claim 31, wherein the projections (71) and depressions (72)of the distribution area (34) are designed in such a way that the thirdcontact surfaces (74) obtain an approximate line shape when the heatexchange plate (11) is provided in the plate package (10) adjacent toanother heat exchanger plate (11).
 33. A pair of heat exchanger platescomprising a first heat exchanger plate (11) and a second heat exchangerplate (11), which are adapted to abut each other in a plate package fora plate heat exchanger for receiving a first medium and a second medium,wherein each of the heat exchanger plates (11) has a central extensionplane (p-p) and comprises a first end area (31), a second end area (32),a central heat transfer area (33), which extends between the first endarea (31) and the second end area (32), wherein a center axis (x)extends along the heat exchanger plate through the first end area (31),the central heat transfer area (33) and the second end area (32), and atleast a first distribution area (34) which extends on the first end area(31) and adjoins the central heat transfer area (33) along a borderline(35), wherein the distribution area (34) in relation to the extensionplane (p-p) has projections (71) and depressions (72) which are adaptedto abut depressions (72) and projections (71), respectively, on adistribution area (34) of adjacent heat exchanger plates in the platepackage for providing a uniform distribution of said media along theborderline (35), wherein the central heat transfer area (33) in relationto the extension plane (p-p) has projections (51) and depressions (52)which are adapted to abut depressions (52) and projections (51),respectively, on a central heat transfer area (33) of adjacent heatexchanger plates (11) in the plate package (10) for forming firstcontact surfaces (54) which are positioned at a first distance (A3) fromeach other along a first direction which is substantially parallel withthe borderline (35), and wherein the central heat transfer area (33) ofat least the first heat exchanger plate (11) comprises at least a firsttransition area (58), which adjoins the first distribution area (34)along the borderline (35) and which in relation to the extension plane(p-p) has projections (61) and depressions (62) which are adapted toabut depressions (62, 52) and projections (61, 51), respectively, of acentral heat transfer area (33) of the second heat exchanger plate (10)for forming second contact surfaces (64) which are positioned at asecond distance (A4) from each other along said first direction which issubstantially parallel with the borderline (35), wherein the seconddistance (A4) is significantly shorter than the first distance (A3). 34.A pair of heat exchanger plates according to claim 33, wherein thecentral heat transfer area (33) of the first heat exchanger plate (11)has a corrugation, which forms said projections (51) and depressions(52) and which extends along an inclination direction forming an acutefirst angle (α) with the center axis (x), wherein the first transitionarea (58) has a corrugation, which forms said projections (61) anddepressions (62) and which extends along an inclination directionforming an acute second angle (β) with the center axis (x), and whereinthe first angle (α) is significantly larger than the second angle (β).35. A pair of heat exchanger plates according to claim 33, wherein thecentral heat transfer area (33) of the second heat exchanger plate (11)comprises at least a first transition area (58), which adjoins the firstdistribution area (34) along the borderline (35) and which in relationto the extension plane (p-p) has projections (61) and depressions (62)which are adapted to abut depressions (62) and projections (61),respectively, of the first transition area (58) of the first heatexchanger plate (11) for forming said second contact surfaces (64) whichare positioned at a second distance (A4) from each other along saidfirst direction which is substantially parallel with the borderline(35), wherein the second distance (A4) is significantly shorter than thefirst distance (A3).
 36. A pair of heat exchanger plates according toclaim 33, wherein at least some of the second contact surfaces (64) areprovided along at least a line which extends in parallel with theborderline (35) and is located at a distance (B1) from the borderline(35), which distance is relatively small and significantly shorter thanthe second distance (A4).
 37. A pair of heat exchanger plates accordingto claim 33, wherein said first direction extends substantiallyperpendicularly to the center axis (x).
 38. A pair of heat exchangerplates according to claim 33, wherein the projections (61) anddepressions (62) of the transition area (58) are designed in such a waythat the second contact surfaces (64) obtain an approximate point shape.39. A pair of heat exchanger plates according to claim 33, wherein theprojections (71) and depressions (72) of the distribution area (34) ofthe first heat exchanger plate (11) abut depressions (72) andprojections (71), respectively, of the adjacent second heat exchangerplate (11) for forming third contact surfaces (74).
 40. A pair of heatexchanger plates according to claim 39, wherein the projections (71) anddepressions (72) of the distribution area (34) are designed in such away that the third contact surfaces (74) obtain an approximate lineshape.
 41. A pair of heat exchanger plates according to claim 33,wherein the second heat exchanger plate (11) is turned 180° in relationto the first heat exchanger plate (11) in the extension plane (p-p). 42.A plate package for a plate heat exchanger for receiving a first mediumand a second medium, which plate package (10) comprises first heatexchanger plates (11) and second heat exchanger plates (11) which areprovided adjacent to each other in an alternating order in the platepackage (10), wherein each of the heat exchanger plates (11) has acentral extension plane (p-p) and comprises a first end area (31), asecond end area (32), a central heat transfer area (33), which extendsbetween the first end area (31) and the second end area (32), wherein acenter axis (x) extends along the heat exchanger plate through the firstend area (31), the central heat transfer area (33) and the second endarea (32), and at least a first distribution area (34) which extends onthe first end area (31) and adjoins the central heat transfer area (33)along a borderline (35), wherein the distribution area (34) in relationto the extension plane (p-p) has projections (71) and depressions (72)which are adapted to abut depressions (72) and projections (71),respectively, on a distribution area (34) of adjacent heat exchangerplates (11) in the plate package (10) for providing a uniformdistribution of said media along the borderline (35), wherein thecentral heat transfer area (33) in relation to the extension plane (p-p)has projections (51) and depressions (52) which are adapted to abutdepressions (52) and projections (51), respectively, on a central heattransfer area (33) of adjacent heat exchanger plates (11) in the platepackage (10) for forming first contact surfaces (54) which arepositioned at a first distance (A3) from each other along a firstdirection which is substantially parallel with the borderline (35), andwherein the central heat transfer area (33) of at least the first heatexchanger plates (11) comprises at least a first transition area (58),which adjoins the first distribution area (34) along the borderline (35)and which in relation to the extension plane (p-p) has projections (61)and depressions (62) which are adapted to abut depressions (62, 52) andprojections (61, 51), respectively, of a central heat transfer area (33)of adjacent heat exchanger plates (11) for forming second contactsurfaces (64) which are positioned at a second distance (A4) from eachother along said first direction which is substantially parallel withthe borderline (35), wherein the second distance (A4) is significantlyshorter than the first distance (A3).
 43. A plate package according toclaim 42, wherein the central heat transfer area (33) of the first heatexchanger plates (11) has a corrugation, which forms said projections(51) and depressions (52) and which extends along an inclinationdirection forming an acute first angle (α) with the center axis (x),wherein the first transition area (58) has a corrugation, which formssaid projections (61) and depressions (62) and which extends along aninclination direction forming an acute second angle (β) with the centeraxis (x), and wherein the first angle (α) is significantly larger thanthe second angle (β).
 44. A plate package according to claim 42, whereinthe central heat transfer area (33) of the second heat exchanger plates(11) comprises at least a first transition area (58), which adjoins thefirst distribution area (34) along the borderline (35) and which inrelation to the extension plane (p-p) has projections (61) anddepressions (62) which are adapted to abut depressions (62) andprojections (61), respectively, of the first transition area (58) of thefirst heat exchanger plates (11) for forming said second contactsurfaces (64) which are positioned at the second distance (A4) from eachother along said direction which is substantially parallel with theborderline (35), wherein the second distance (A4) is significantlyshorter than the first distance (A3).
 45. A plate package according toclaim 42, wherein at least some of the second contact surfaces (64) areprovided along at least a line which extends in parallel with theborderline (35) and is located at a distance (B1) from the borderline,which distance is relatively small and significantly shorter than thesecond distance (A4).
 46. A plate package according to claim 42, whereinsaid first direction extends substantially perpendicularly to the centeraxis (x).
 47. A plate package according to claim 42, wherein theprojections (61) and depressions (62) of the transition area (58) aredesigned in such a way that the second contact surfaces (64) obtain anapproximate point shape.
 48. A plate package according to claim 42,wherein the projections (71) and depressions (72) of the distributionarea (34) of the first heat exchanger plates (11) abut depressions (72)and projections (71), respectively, of the adjacent second heatexchanger plates (11) of the plate package (10) for forming thirdcontact surfaces (74).
 49. A plate package according to claim 48,wherein the projections (71) and depressions (72) of the distributionarea (34) are designed in such a way that the third contact surfaces(74) obtain an approximate line shape.
 50. A plate package according toclaim 42, wherein the second heat exchanger plates (11) are turned 180°in relation to the first heat exchanger plates (11) in the extensionplane (p-p).